The present invention generally relates to a nickel based superalloy composition. The present invention also relates to a component comprising a nickel based superalloy composition.
Nickel based superalloys have been extensively used in manufacturing gas turbine engine components. Gas turbine engines having hotter exhaust gases and which operate at higher temperatures are more efficient. To maximize the efficiency of gas turbine engines, attempts have been made to form gas turbine engine components, such as turbine discs, having higher operating temperature capabilities. In particular, there is considerable commercial interest in superalloys for turbine and compressor disk applications which exhibit strength and creep resistance at relatively high temperatures (e.g., 1300-1500° F.), as well as resistance to fatigue crack initiation at the lower temperatures (e.g., 500-1100° F.) often experienced in compressor and turbine disk bores. Higher temperature dwell crack growth resistance is also a significant parameter.
The previous generation of higher temperature capability disk alloys of the prior art are limited to about 1200-1300° F. operating temperature, and include such commercially used alloys as P/M Astroloy, Rene' 88 DT, and IN100. Such disk alloys, including the most recent generation of alloys, are typically made by inert gas atomization into powder form. The powder is subsequently screened to an appropriate size range and consolidated by hot compaction or by hot isostatic pressing (HIP). The consolidated powder is then extruded into a form suitable for isothermal forging into a shape that can be machined into an engine component. Components may also be formed by hot isostatic pressing (HIP) without the extrusion and isothermal forging steps, and subsequently machined to final shape. These methods of manufacture are common throughout the industry for high gamma prime volume fraction disk alloys.
U.S. Pat. No. 6,521,175 B1 to Mourer, et al. discloses a nickel based superalloy which contains 1.9 to 4.0 wt. % tungsten. The superalloy of Mourer, et al. sacrifices some low-temperature dwell fatigue crack growth performance to achieve improved creep performance.
As can be seen, there is a need for a nickel based superalloy composition which exhibits enhanced fatigue crack initiation life at temperatures of 500 to 1200° F., as well as enhanced resistance to creep at temperatures of 1200 to 1450° F. Dwell crack growth resistance at these higher temperatures (1200 to 1450° F.) is also of importance.